Local observable for linear lattice imperfections in circular accelerators

Finding a truly local observable for perturbations of the linear beam dynamics is a nontrivial task, contrary to the nonlinear regime, where local resonance driving terms already exist. The phase beating between two locations depends on errors outside of this region. However, phase advances between four nearby locations can be arranged in a way to cancel the contributions from errors outside of this region up to first order. The resulting local observable contains valuable information about quadrupolar lattice imperfections. This report seeks to explore this local phase beating observable and to test its usefulness for gaining insight in the linear optics imperfections of a circular accelerator.